by Rosemarie Makhmaltchi

Created on: January 13, 2007

In 1970, Xerox's Palo Alto Research Center (PARC) was founded in California. The facility has created dozens of revolutionary devices, including laser fax machines, digital printers, mainframe computers, and the Ethernet. PARC also pioneered several technologies that shaped the way we use computers today. Many of those technologies are related to the 1973 Xerox Alto. The Alto was the first system deliberately designed to be customizable and adaptable to the user's taste the first personal computer. The Alto did not bring new hardware, as it was pieced together in three months from components of other PARC systems, but it fostered an environment where trail-blazing software was developed. Innovative programs made the Alto a popular system, and it was used in places like Sweden's government-owned telephone company and the Carter White House. The following sections describe some of the Alto's innovations.

Display-> In the 1970's some computers displayed alphanumeric characters using a separate device called a character generator. Character generators displayed custom fonts by storing each character in a piece of memory until it was called to the screen. The Alto was the first computer to utilize a bitmap - a block of memory in which each bit corresponded to a dot on the display screen. The first bitmap was monochromatic a bit that was turned "on" caused the corresponding display dot to light up, and a bit that was "off" resulted in an unlit dot on the screen. Turning bits on in a pattern created images on the screen, such as custom fonts. So as not to unduly tax its memory, the Alto was programmed to omit blank places (such as margins) from the bitmap when it displayed a document. The image on screen would also shrink in size as the document filled the memory and left little for the display to work with, but at least now the computer could process its own fonts, without the help of a separate device.

BitBlt-> The invention of the bitmap opened a world of possibility for computer display screens. PARC scientists, in particular Alan Kay, envisioned users being able to draw in a paint program while simultaneously writing a memo. Kay used the analogy of papers piled on top of a desk and figured the idea could work equally well on the Alto. The papers, or "windows," would have to be movable and enable the user to bring any one to the top of the "pile" instantly. Kay's research team at PARC could already tile and even overlap windows on the Alto's screen. But, moving

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